Retrieval of Parameters of Constrained Gamma Raindrop Size Distribution in South China.

Raindrop size distributions (RSDs) retrieved from polarimetric radar observations have proven to be effective for understanding precipitation microphysics. However, the current RSD retrieval scheme from polarimetric radar observations (using radar reflectivity ZHH and differential reflectivity ZDR) in South China has been established for monsoon precipitation only. Using abundant RSD observations from 2D video disdrometers (2DVDs), this study constructs the high-precision shape–slope (μ–Λ) relationships of the constrained gamma (C-G) model for subgroups of ZHH and ZDR for not only monsoon but also premonsoon, typhoon, and dry seasons. The current RSD retrieval is only applicable for precipitation with rain rate: R > 5.0 mm h−1, and total raindrop number concentration: Nt > 1000 m−3. This study expanded the applicability of rain rate and number concentration with R > 0.5 mm h−1 and Nt > 100 m−3. The new retrieval scheme was tested in four typical rainfall cases and provided better accuracy in estimating mass-weighted mean diameters and normalized intercept parameters. The new scheme was also better suited for analyzing precipitation microphysics in South China, which helps to gain a better understanding of microphysics in various types of precipitation in this region. [ABSTRACT FROM AUTHOR]